Halogenated benzenephosphonate esters



United States Patent Oflice 3,384,684 Patented May 21, 1968 3,384,684 HALOGENATED BENZENEPHOSPHONATE ESTERS Robert H. Boschan, Los Angeles, and James P. Holder,

Woodland Hills, Calif assignors, by mesne assignments, to McDonnell Douglas Corporation, Santa Monica, Calif., a corporation of Maryland No Drawing. Filed Dec. 28, 1964, Ser. No. 421,651 10 Claims. (Cl. 260-961) ABSTRACT OF THE DISCLOSURE Halogenated, e.g., fluoroor chloro-substituted diaryl, particularly monofluoro or monochloro-phenyl phenyl, benzenephosphonates, useful particularly at elevated temperatures as hydraulic fluids, additives for hydraulic fluids, lubricants and heat transfer or cooling media, for aircraft systems and for industrial use.

This invention relates to certain halogenated aryl benzenephosphonate esters and is particularly concerned with the provision of novel chloro and fluoro diaryl benzenephosphonates.

It is an object of the present invention to provide a series of compounds having high fire resistance, high temperature stability, and which remain in liquid form over a relatively wide temperature range and are relatively nonvolatile at elevated temperatures.

Another object of the invention is the provision of novel fluorinated diaryl, particularly fluorinated diphenyl, benzenephosphonates and chlorinated diaryl, particularly chlorinated diphenyl, benzenephosphonates having the above-noted properties and other advantages, and having utility as hydraulic fluids, heat transfer fluids, and lubricants, particularly at elevated temperatures, and as additives for hydraulic fluids, heat transfer media and lubricants.

Other objects and advantages will appear hereinafter.

We have discovered that the above-noted objects are achieved according to the invention by the provision of a class of halogenated diphenyl benzenephosphonates having the formula:

ll CaH P where R is a member selected from the group consisting of monofluorophenyl and monochlorophenyl, and R is a member selected from the group consisting of phenyl, cresyl and xylyl.

The fluorine or chlorine substituents on the monofluorophenyl or monochlorophenyl group can be carried in ortho, meta or para position on the phenyl nucleus with respect to the attachment of such nucleus to the oxygen atom of the phosphonate ester. However, the meta and para derivatives generally are preferred. Also, the fluorinated derivatives generally have greater stability at higher temperatures as compared to the corresponding chlorinated derivatives.

The preferred phosphonate esters of the invention are the compounds having the general formula where X is a member selected from the group consisting of fluorine and chlorine, with X preferably being in meta position on the phenyl nucleus.

It has been found that the above-defined halogenated phosphonates, particularly the halogenophenyl phenyl benzenephosphonates are valuable as functional fluids, e.g., as base stocks for hydraulic fluids, as heat transfer media, and as lubricants, particularly at elevated temperatures, e.g., above about F., due to the advantageous physical properties of such compounds, including high fire resistance and increased temperature stability. Thus, for example, generally these fluorinated and chlorinated phosphonate esters have a thermal stability in the range of about 600 to about 800 F., and autoignition temperatures of the order of about 900 to about 1,000 F. These compounds are also relatively non-volatile at elevated temperatures due to the high boiling point of these materials. Moreover, the phosphonate esters of the invention have good hydrolytic stability and do not adversely affect materials, such as metals, e.g., steel, aluminum, and the like, with which they may be in contact.

The above-noted properties render many of the halogenated phosphonate esters hereof, and especially the halogenphenyl phenyl derivatives defined above, useful as hydraulic fluids, lubricants and heat transfer media, e.g., cooling fluids, in aircraft systems at moderately elevated temperatures.

The fluoro and chloro phosphonate esters of the invention also can be employed as general industrial hydraulic fluids and lubricants particularly where high fire resistance and high thermal stability are important characteristics, e.g., in high pressure systems, such as hydroelectric turbines, air compressors and hydraulic presses having various sources of ignition, which would result in fire and explosion from leaking hydraulic fluids in the event such fluids are not adequately fire resistant.

Also, the chloro and fluoro substituted phosphonate esters according to the invention can be employed as additives, for example, in combination with each other or with compatible phosphate or phosphonate esters in which they are miscible such as the pentafluorophenyl substituted phosphate esters of the copending application Ser. No. 364,787, filed May 4, 1964, of Seil et al., now US. Patent 3,341,631, or the fluorinated diaryl phosphate esters of the copending application Ser. No. 364,763, filed May 4, 1964, of Seil et al., now US. Patent No. 3,308,207. When so employed, the compounds of the invention can function as base stock components, thickeners, lubricity improvers, or pour point depressants in the base stock, e.g., the phosphate or phosphonate esters in which the invention compounds are incorporated. When employed as additives, the benzenephosphonate esters of the invention are used generally in a proportion of about 1 to about 10% by weight of the total composition including base stock. However, when employed as base stock components in such mixtures, the halogenated phosphonates of the invention can be employed in substantially larger amounts.

The halogenophenyl aryl, e.g., phenyl, benzenephosphonates of the invention are produced according to one convenient mode of procedure by reacting a mixture of the corresponding monohalogenated, e.g., monochloro or monofluoro phenol, and nonhalogenated phenol, e.g., phenol itself, with benzene phosphonyl dichloride, employing approximately equimolar amounts of all three reactants, preferably in the presence of pyridine or any other suitable HCl acceptor. The proportion of HCl acceptor or pyridine generally employed is usually about equimola-r with respect to the total molar proportion of phenols present. The mixture is then heated at reflux for a period of hours, and is then cooled and a relatively large volume of water added. The mixture separates into an organic phase and an aqueous phase, and the organic phase containing the phosphonate ester product is withdrawn. The aqueous layer is extracted with a solvent such as ether to remove organic values and the ether extract is added to the main organic layer withdrawn. The remaining organic reaction mixture is washed and then dried with a drying agent such as anhydrous magnesium sulfate. Solvents are removed by distilling at reduced pressure, and the remaining mixture is distilled at still lower pressure to recover the desired monohalogenophenyl aryl benzenephosphonate compounds.

Alternatively, such phosphonates can be prepared by reacting one such phenol, e.g., phenol itself, with benzene phosphonyl dichloride in approximately equimolar proportions to replace one of the chlorine atoms of the phosphonyl dichloride, and then reacting the other phenol, e.g., monofiuorophenol, with such intermediate phosphonyl chloride in approximately equimolar proportions.

Examples of halogenophenyl aryl benzenephosphonate esters according to the invention are as follows:

I? i can? cum o@-1r 0 O El 06ml o -o1 0 can r o r I CH;

(1)) 1 o 1 H C llgl C Ila CII3 CH; CI[;;

The following are examples of preparation and use of the invention compounds:

EXAMPLE 1 m-Chlorophenyl phenyl benzenephosphonate To 29.6 g. (0.315 mole) of phenol, 40.5 g. (0.315 mole) of m-chlorophenol and 52.2 g. (0.66 mole) of pyridine in 250 ml. of benzene was added dropwise with stirring 58.5 g. 0.30 mole) of benze-nephosphonyl dichloride. The temperature was maintained at 20-25 C. during the addition, which was complete in 15 minutes. The mixture was then heated and refluxed for 16 hours.

The mixture was cooled and poured into 400 ml. of water, and the upper organic layer was removed. The aqueous layer was extracted with three ml. portions of ether, and the ether extracts were added to the organic layer. The organic layer was washed with successive 100 ml. portions of 5% hydrochloric acid, 5% sodium bicarbonate, and water, then with two 50 ml. portions of Water. The organic layer was dried over anhydrous magnesium sulfate and filtered. The solvents were removed by evaporation on a steam bath.

The residue was distilled at reduced pressure; the main product fraction, 81.1 g. (78.4% yield) distilled at to 199 C. (0.29-0.32 mm. of mercury). The product crystallized slowly on standing, M.P. 34.837.8 C.

The resulting phosphonate ester product, compound (1) above, m-chloro-phenyl phenyl benzenephosphonate, had good thermal stability between about 600 and about 800 F., high autoignition temperature in the range of about 900 to about 1,000 F., good hydrolytic stability and high fire resistance. Such compound is useful as a base stock component for a hydraulic fluid of an aircraft system at temperatures above about 100 F., or as a fire resistant thermally stable hydraulic fluid or lubricant for general industrial purposes, e.g., in a hydraulic press or as a compressor lubricant at moderately elevated temperatures.

EXAMPLE 2 m-Fluorophenyl phenyl benzenephosphonate To 29.6 g. (0.315 mole) of phenol, 35.3 g. (0.315 mole) of m-fluorophenol and 52.2 g. (0.66 mole) of pyridine in 250 ml. of benzene was added dropwise with stirring 58.5 g. (0.30 mole) of benzenephosphonyl dichloride. The temperature was maintained at 2025 C. during the addition, which was complete in 15 minutes. The mixture was then heated and refluxed for 16 hours.

The mixture was cooled and poured into 40 ml. of water, and the upper organic layer was removed. The aqueous layer was extracted with three 100 ml. portions of ether, and the ether extracts were added to the organic layer. The organic layer was washed with successive 100 ml. portions of hydrochloric acid, 5% sodium bicarbonate, and water, then with two 50 ml. portions of water. The organic layer was dried over anhydrous magnesium sulfate and filtered. The solvents were removed by evaporation on a steam bath.

The residue was filtered and 63.5 g. (64.5% yield) of product was obtained. After 3 recrystal'lizations the product melted at 7-1.5-7 2.0 C.

The resulting product, m-fluorophenyl phenyl benzenephosphonate, compound (2) above, has good thermal stability, high autoignition temperature, good hydno-lytic stability and high fire resistance. Such phosphonate is useful as a base stock for a hydraulic fluid or lubricant in a system operating at temperatures in excess of about 150 F.

EXAMPLE 3 p-Fluorophenyl m-cresyl benzenephosphonate The procedure of Example 2 above is substantially carried out but employing meta cresol and p-fluorophenol instead of phenol and m-fluorophenol, respectively.

The resulting product, compound (7) above, p-fluorophenyl rn-cresyl benzenephosphonate, has good thermal stability, high autoignition temperature, good hydrolytic stability and high fire resistance. Such phosphonate is useful as a hydraulic fluid or lubricant or as a component or additive to a phosphate ester base stock.

EXAMPLE 4 o-Chlorophenyl p cresyl benzenephosphonate The procedure of Example 1 above is carried out except that there is employed para cresol and o-chlorophenol instead of phenol and m-chlorophenol, respective'ly.

The resulting product, compound (8) above, o-chlorophenyl p-cresyl benzenephosphonate, has good thermal stability, high autoignition temperature, good hydrolytic stability and high fire resistance.

EXAMPLE 5' A mixture is prepared consisting of 95% by weight of bis'(pentafiuorophenyl)butyl phosphate and 5% by weight of the compound produced in Example 1 above, m-chlorophenyl phenyl 'benzenephosphonate.

T-he butyl phosphate ester noted above is described and claimed in the above copending application Ser. No. 364,787 of Seil et al., now U.S. Patent 3,341,631, and is useful as a base stock for a hydraulic fluid of an aircraft system. The resulting mixture of this compound together with the compound of Example 1 hereof employedas additive, has the advantageous properties of the butyl phosphate ester, and in addition has improved lubricity and reduced pour point. Such mixture is effective as a hydraulic fluid and lubricant.

EXAMPLE 6 About 92.5% of 1,l,5-trihydroperfluoropentyl diphenyl phosphate and 7.5% by weight of the compound of Example 2 above, m-fluorophenyl phenyl benzenephosphonate, are mixed. The diphenyl phosphate ester is described and claimed in the above copending application Ser. No. 364,763, now US. Patent No. 3,308,207, of Seil et al. and is indicated therein as useful as a hydraulic fluid of an aircraft system. The resulting mixture containing the additive of Example 2 above, has improved lubricity, viscosity characteristics and pour point, as compared to the diphenyl phosphate component alone of the mixture.

From the foregoing, it is seen that the invention provides a novel class of halogenated, e.g., fluoroor chlorosubstituted diaryl, particularly monofluoroor monochlorophenyl phenyl, benzenephosphonates which are useful particularly at elevated temperatures as hydraulic fluid base stocks, or as base stock components or additives for hydraulic fluids, lubricants and heat transfer or cooling media, for aircraft systems and for industrial use.

While we have described particular embodiments of our invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

We claim:

1. A phosphonate having the formula OOR Where R is a member selected from the group consisting of monofluorophenyl and monochlorophenyl, and R is a member selected from the group consisting of phenyl, cresyl and xylyl.

2. A phosphonate as defined in claim 1, wherein R is monofluorophenyl and R is phenyl.

3. A phosphonate as defined in claim 1, wherein R is monochlorophenyl and R is phenyl.

4. A phosphonate as defined in claim 1, wherein R is monofluorophenyl and R is cresyl.

5. A phosphonate as defined in claim 1 wherein R is monochlorophenyl and R is cresyl.

6. A phosphonate as defined in claim 1, wherein said fluorine and chlorine substituents are in meta position in the phenyl nucleus.

7. m-Chlorophenyl phenyl benzenephosphonate.

8. m-Fluorophenyl phenyl benzenephosphonate.

9. p-Chlorophcnyl phenyl benzenephosphonate.

10. p-Fluorophenyl phenyl benzenephosphonate.

References Cited UNITED STATES PATENTS 2,632,018 3/1953 Kosolapoif 260-961 3,054,821 9/1962 Rolih et al. 26096l XR 3,071,609 1/1963 Campbell et al. 260961 XR 2,769,743 11/1956 Mattson 167-30 CHARLES B. PARKER, Primary Examiner.

A. H. SUTTO, Assistant Examiner. 

